1. Field of the Invention
The present invention relates generally to complex fluids. More specifically, the present invention concerns a complex fluid that includes a conductive medium and micronparticles suspended therein, wherein each micronparticle includes a magnetically permeable core coated by an electrically insulating material and a conductive winding there around so that when a current is passed through the fluid, it “flows” along the windings inducing an electromagnetic field around each micronparticle, thereby affecting the properties of the fluid.
2. Discussion of Prior Art
There are a wide range of complex fluids known in the art. One particular class of these fluids includes “smart fluids.” Certain types of smart fluid are known to change viscosity in the presence of certain external forces. For example, electrorheological (ER) fluids and magneto-rheological (MR) fluids are known colloidal suspension of particles that respond to either an electrical or magnetic field external to the fluid. ER and MR fluids are known to exhibit a marked increase in viscosity in the presence of electrical and magnetic fields, respectively. This change in viscosity is extremely rapid (e.g., 1-10 milliseconds). When the external field is removed, these fluids return to their original state. It is known in the art to use these fluids as working fluids for various machines and apparatus such as dampers, actuators, ink-jet color recording, and the like.
However, all of these prior art complex fluids suffer from several undesirable problems and limitations. For example, while it is known that ER and MR fluids allow rapid changes in apparent viscosity in the presence of electrical and magnetic fields, these effects are dependent upon the fields external to the fluid. In this regard, the distance into the fluid over which the rheological properties hold is undesirably limited. That is, the effects are greatest at close proximity to the origin of the external field and diminish moving further into the fluid and further away from the origin of the field. In addition, ER and MR fluids are not able to exert a force in and of themselves. That is, these fluids have particles that align due to an external field, but cannot exert a force in and of themselves. These problems and limitations render these prior art fluids poorly suited for certain applications. Accordingly, there is a need for an improved complex fluid that does not suffer from these problems and limitations.